Process for the manufacture of a supraconductive wire



United States Patent Office Patented June 14, 1966 7 Claims. (cl. 148-2)This invention relates to a process for the manufacture of asupraconductive wire, particularly of a wire of intermetallic compounds.

As is known, supraconductivity of metallic materials, ie the sudden dropin electric resistance in the range of low temperatures, particularlynear absolute zero, is not limited to specific pure metals or to alloysof two supraconductors. Alloys of a normal conductive material and asupraconductive material and alloys of two norinal conductive materialsshow supraconductivity as Wel Intermetallic compounds gained particularimportance as supraconductors since their transition temperaturesmarkedly exceed those of the pure components. Known intermetalliccompounds having supraconductivity are chiefly those of the metalsniobium, vanadium and tantalum, e.g. the compounds Nb Sn, Nb Al, Nb lnand Nb Ga, V Si, V 62. and V Sn as well as Ta Sn. In particular, thesesupraconductors are widely used for production of strong magnetic fieldswith both direct current and alternating current.

The present invention is based on the problem to simplify themanufacture of supraconductive wires of intermetallic compounds, whichmanufacture is faced with great difiiculties due to the brittleness ofthese compounds, while simultaneously bringing about the filamentstructure which is essential forthe use of supraconductors.

It is already known to manufacture wires of the intermetallic compoundNb Sn by filling a tube of niobium.

either with a mixture of powdered Nb Sn and an excess of tin powder orwith a still reactive mixture of tin and niobium powders, sealing thetube with a niobium plug and reducing it to the Wire diameter desired bymechanical Working. Following this, the wire is annealed at temperaturesof between 970 and 1400 C. certain number of filaments is developed inthis prior art process, it has been found that a substantial increase inview of the properties of the supraconductive Wire is desirable.

A surprising solution to the problem on which the invention is based isthe manufacture of a supraconductive wire, particularly of intermetalliccompounds, by density filling a tube made of one of the components ofthe intermetallic phase with a wire bundle of the same material, fillingthe voids with the second component of the intermetallicphase in fusedstate, drawing down the shaped body while cold to the diameter desiredusing preferably several steps, winding it, e.g. into a coil, for finalshaping and finally annealing it. This will give the wire thesupraconductive characteristics.

The particular advantage of this process consists in While a that thewire bundle consisting of the one component of connection with themanufacture of a supraconductive wire consisting of the intermetallicphase Nb Sn with the ratio of tube and wire to the amount of tin fillingthe voids being chosen in accordance with the resultant compound Nb Sn.Wires of other intermetallic compounds may be manufactured in ananalogous manner so that this example does not constitute a limitationof the subject matter of this application. For example, the material forthe tube and the wire bundle may be vanadium and the second component ofthe intermetallic phase may be gallium. Moreover, it is to be understoodthat the manufacture of a wire of an intermetallic compound or alloyconsisting of more than two components is also possible by the processof the invention.

A niobium tube of 50 cm. in length and 10 mm. in outside diameter andbeing pickled in its interior is electroplated in its interior with atin layer of 15 microns thickness. Niobium wires each having a diameterof 0.5 mm. are tin-plated by the dipping process, combined into a bundleand drawn through a wire die thereby adapting the diameter of the totalbundle to the inside diameter of the niobium tube. After the wire bundlehas been drawn into the niobium tube, the latter is purged with inertgas, dipped into fused pure tin and the molten tin is sucked into thetube with the use of vacuum. Desirably the tube is then left for sometime in the molten tin and thereafter V the tube is cold-drawn inseveral steps to the wire diameter desired of, for example, 0.1 mm. The'wire is then wound into a coil and annealed for several hours attemperatures of between about 900 and 1200 C.

The wires of intermetallic compounds manufactured by the process of theinvention have considerably improved properties as compared with wire ofNb Sn manufactured by the prior art process and result in substantialadvantages when used for the production of high magnetic fields,particularly for the control of electron and ionic currents.

What is claimed is:

1. A process for the manufacture of a supraconductive wire, particularlyof a wire consisting of intermetallic compounds, which comprises denselyfilling a tube made of the one component of the supraconductiveintermetallic phase with a wire bundle preferably consisting of the samematerial, filling the voids with the second component of theintermetallic phase in molten state, drawing down the shaped body to thediameter desired and annealing it after final shaping.

2. The process of claim 1, wherein said filling of the voids with saidsecond component of the intermetallic phase is effected with theapplication of vacuum.

3. The process of claim 1, wherein said drawing-down to the finaldiameter is effected cold in several steps.

4. The process of claim 1, wherein said wire is wound into a coil beforeannealing.

5. The process of claim 1, wherein the material of the tube and wirebundle is niobium.

6. The process of claim 1, wherein said second component of theintermetallic phase is tin.

7. The process of claim 1, wherein said annealing is eifected forseveral hours at a temperature between about 900 and 1200 C.

References Cited by the Examiner UNITED STATES PATENTS 3/1964 Buehler eta1. 174 X 12/1964 Wong 75-528 X

1. A PROCESS FOR THE MANUFACTURE OF A SUPRACONDUCTIVE WIRE, PARTICULARLYOF A WIRE CONSISTING OF INTERMETALLIC COMPOUNDS, WHICH COMPRISES DENSELYFILLING A TUBE MADE OF THE ONE COMPONENT OF THE SUPRACONDUCTIVEINTERMETALLIC PHASE WITH A WIRE BUNDLE PREFERABLY CONSISTING OF THE SAMEMATERIAL, FILLING THE VOIDS WITH THE SECOND COMPONENT OF THEINERMETALLIC PHASE IN MOLTEN STATE, DRAWING DOWN THE SHAPED BODY TO THEDIAMETER DESIRED AND AN NEALING IT AFTER FINAL SHAPING.